Lead levels in Dillon water again exceed federal limit
November 7, 2016
Testing conducted by the town of Dillon last month again found lead levels in some homes that exceeded the 15 parts per billion (ppb) limit set by the Environmental Protection Agency. The new results, which found elevated lead levels in four of 20 homes tested, mark the third time since 2012 that the town has been over the federal limit for lead concentrations in drinking water.
Lead is a neurotoxin that can be particularly harmful to children and pregnant women, presenting a host of mental and physical impairments ranging from lowered IQ to kidney problems. Congress amended the Safe Drinking Water Act in 1986 to include lead, but older homes with lead solder in their pipes and fixtures are still at risk.
Dillon was first alerted to a lead problem in 2012, when tests showed concentrations as high as 92 ppb. Although no lead has been found in Dillon's source water, the tests prompted the town to install a $30,000 system to raise the pH of the water and hopefully limit lead corrosion from older pipes.
That led to some reductions, but October's tests — which targeted higher-risk homes built between 1983 and 1987 — revealed that, at 26 ppb, some of the town's homes are still exceeding the federal limit.
Pb per billion
While the health risks of lead are well known, there isn't a consensus on exactly how much is too much, said Greg Kail, communications director for the Denver-based American Water Works Association.
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"Public health officials can't identify a safe level, so the best thing to do is minimize risk as much as possible," he said.
"When we test, we are mandated to look at areas that pose a higher risk, sites with older plumbing that are more likely to have materials containing lead," said Dillon public works director Scott O'Brien. "Typically, what we have found is that older plumbing with lead-based solder — usually before 1988 — and some faucets made with brass or bronze components tend to be the contributors to lead in finished drinking water in homes and buildings."
"Lead is a totally different animal because it's in the home environment," said Kail. "Its source is something in the household, which is why one home could have lead and another next door could not."
Utilities are required to routinely test for lead, and it's a red flag when the 90th percentile of samples exceeds 15 ppb.
"That's a trigger for the utility to evaluate corrosion control, notify customers and make changes," Kail said. "A utility can't know whether or not a home has lead pipes, but it can take steps to adjust the chemistry of the water to reduce the likelihood that lead will leach."
A pH problem
That's the approach Dillon took when it installed a pH-increasing system in January 2015, which officials hoped would reduce the likelihood of lead leaching. Over the years, Dillon's water has gone from a pH of 7.8 to 7 for unknown reasons, said O'Brien. The new system bumped that up to 8.
While the town reported initial lead reductions, the EPA requested a bigger sample size that included more high-risk homes. Those results indicated that lead was still a problem.
"The only thing we can do at this time is raise the pH," said Robert Buras, chief plant operator for Dillon's water system. "We'll be raising it 8.5, and that's basically our limitation with that process. We're also going to be working with engineering consultants and the state."
If the higher pH doesn't do the trick, Buras said the town would likely change the chemical it uses to modify the pH from sodium hydroxide to lime or soda ash. Both increase the "hardness" of the water — or how many molecules are dissolved in it — and make it harder for lead to leach in.
"In a broad sense, altering the chemistry has been a very effective strategy for lowering lead in past decades," said Kail. "But in order to completely remove the risk, you need to remove the source."
That can difficult, however, because the sources of lead are almost invariably the privately owned pipes and fixtures in peoples' homes. What's more, homeowners and utility companies alike rarely know what homes have lead in them; records of what types of pipes were used in homes weren't kept until the danger of the chemical became apparent and it was banned.
The AWWA estimates that there are some 6.1 million leaded service lines left in the country, and they can cost roughly $5,000 to replace. If you're concerned that you may have a lead service line, Kail recommends calling a plumber to test the line or the water coming from your tap.